Galaxy M83

Designation:       Messier 83, NGC 5236
Constellation:Hydra
Magnitude: +7.1
Apparent size:13.6′ x 13.2′
Diameter:63,000 light years
Distance:16 million light years
Date:2020-06-19
Exposure:49 x 179 sec = 2 hrs 46 min
Field of View:37.7 x 37.5 arcmin; Up is 261° E of N

Visible in both hemispheres – although we get a better view here in the South – M83 is a barred spiral galaxy and one of the brightest in our hemisphere.

In this two and a half hour exposure it displays a bright core and a less well defined bar, from which emerge three clearly defined spiral arms. One is short and two are longer and they contain numerous dark lanes, star fields and nebulosities.

M83 is notable for six supernovae, which were observed between 1923 and 1983.


The Cosmos is all that is or ever was or ever will be.

Carl Sagan

I took 62 sub-images of M83 during this session but thirteen were rejected by the brightness filter, so out of 185 minutes of imaging I picked up 146 minutes of data in forty-nine subs:

2020-06-19 M83 End of Session. The green and red squares above and below the blue line indicate the sub-frames which were accepted and rejected by the SharpCap brightness filter due to the passing high clouds.
2020-06-19 M83 End of Session. The green and red squares above and below the blue line indicate the sub-frames which were accepted and rejected by the SharpCap brightness filter due to the passing high clouds.

Nevertheless, almost 2½ hours of exposure was quite satisfying. My friends from Macarthur Astronomical Society who travelled 100 km to a dark sky site that night had to pack up mid-evening due to thick fog, so I was fortunate.


There is still a lot of uncertainty with astronomical distance measurements. For example, statistics in Sky Safari Pro state that M83 is 16 million light years away but in the description on the same page they say 15 million. So I checked around.

Wikipedia says 14.7 million. Wolfram-Alpha puts it at 15.79 million. The Night Sky Observers Handbook (Vol 2) by Kepple and Sanner has it at 22 million. Sometimes doing a bit of research throws up even more confusion!

Simbad includes nine different measurements between 4.47 and 5.16 mega parsecs, which is 14.58 to 16.83 million light years. I give up on researching.

I’m gonna leave it at 16 million …

EDIT (28th June 2020): See comments further below regarding the two faint and tiny galaxies close to M83.

Distant galaxies ESO 444-85 and [R84] A1-342 – adjacent to M83.
Telescope Details
SkyWatcher Esprit 120 mm apochromatic 3-element refractor.
840 mm focal length @ f/7 with field flattener.
Baader L-Booster UHC-S light pollution filter 2458276.
SkyWatcher EQ6-R Pro mount.
Camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx)
ZWO ASI120 guide camera, using PHD2 software.

See annotated image at Astrometry.net

15 Comments

  1. I am always intrigued with the remarkable advancement of amateur astronomy over my lifetime. In that vein, your images are always so compelling. Back nearly 50 years ago (4/13/62 to be exact,) I observed this galaxy from dark skies as part of the Messier quest, simply describing it as round with a central condensation. Imaging was not possible.
    Fast forward to your image. Wow! Today my hobby continues in the background with images like your’s on the computer. Again, I say compelling, but with a large dose of awe as well. In the vein of continuing to explore, I see one, and maybe two potential far, far away galaxes just above (about 20° (right to straight up) of M 83) in your stunning image. Note it, (or they,) are just slightly different from other background stars. Thought????

    Liked by 1 person

    1. Well spotted! I’ve been wondering about those two tiny smudges too.

      I confirmed them in two other independent images and they are definitely real, so – just for the heck of it – I determined the coordinates of the two galaxies, using Google Sky.

      I then entered queries into the Simbad data base and determined that the brighter of the two is galaxy ESO 444-85 with a red shift of 0.01207.

      M83 has a redshift of 0.001733 so ESO 444-85 is much further away.

      According to my Sky Safari app, this object is a 16th magnitude galaxy, 665 million light years away and is also known as PGC 48132. It has a recession velocity of 13,940 km/sec, about 4.6% of light speed.

      The other galaxy identifies as [R84] A1-342 but I didn’t get any info on it. It is probably further away.

      Thanks for prompting me to spend a couple of hours on this!

      By the way, in looking at the original image, there are three other (smaller) potential galaxies too.

      Liked by 1 person

  2. Sorry for your time spent, but I have a feeling you enjoyed it. And, your investigative mythology is like a treaure in intself for my armchair deep (deep) sky curiositys. It’s interesting how a tiny smudge becomes such a jewel. All this is a strong testament to the quality of your “work!” -(passion!) M 🙂

    Like

    1. Thanks for your kind words.

      It’s not the first time I’ve had such smudges in an image but your comment nudged me into identifying them. It’s always worthwhile when we learn something from it – but I am still coming to terms with picking out a galaxy at a distance of 665 million light years….. 😵

      Liked by 1 person

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